Brake indicator



July 20, 1937. R. J. NORTON BRAKE INDICATOR Filed Sept. 20, 1930Patented July 20, 1937 BRAKE INDICATOR.k

Raymond J. Norton, Washington, D. C., assignor to Bendix Brake Company,South Bend, Ind., acorporation of Illinois Application September 20,1930, Serial No. 483,355 2 Claims. (Cl. 177-v-311) This inventionrelates to indicating mechanism for brakes. y

The ordinary brake mechanism comprises a rotating drum and cooperatinginternal expanding non-rotating shoe. To increase the retardation effectthe friction material is interposed between the rotating andnon-rotating parts and in most cases is xed to the shoe. Considered fromthe standpoint of safety the brake mechanism is perhaps the mostimportant structure on an automotive vehicle. It is, therefore,important to know the condition of the brake lining because this factorAin a large measure determines the efficiency of the brake. When thebrake lining is worn down to an undesirable thinment. i r

Heretofore the estimation of the condition of the brake lining has beena matter of mere chance. The present invention consists broadly of theidea of the provision of means to indicate the condition of Wear of thebrake band.

The main object of the present invention,

therefore, is to provide an instrument for indicating the condition ofthe brakes.

Another object is to provide a dash board indicator adapted to show thecondition of wear of the brake band.

Another object is to provide an indicator positioned in a readilyavailable place to show the condition of the brakes.

Another object is to provide an optical indicator to show the conditionof all of the brakes on an automotive vehicle.

With these` and other equally important objects in view the inventioncomprehends the concept of associating with one or more of the brakes ofa vehicle an indicator, preferably an electrical indicator, which showsthe condition fied form;

Figure 3 is a circuit diagram showing the relationship of the indicatingmeans to the Vbrakes l on the vehicley and Figure 4 is a detailedshowing of the dial of the indicating instrument.

As indicated above, the object of the invenf tion is to provide anindicator for showing the extent of the wear of the brake linings. Thismay be done by positioning an indicator upon the dash board. andoperating this by means of the relative displacement of the brake shoe.The displacement of the latter, upon application of the brakes, dependsupon the extent to which the lining has worn down. While there areanumber of methods of showing such displacement the preferred embodimentselected for illustration involves the use of an electrical current.

As shown in the drawing and particularly in Figure 1, the apparatus maycomprise the brake L drum I, of any conventional form, with which isassociated the non-rotating expansion shoes' 2. Ailixed to the shoe is alining 3. 'I'he drum is sealed olf, against the admission of dust andwater by the backing plate 4.

When such brakes are applied the shoe 2 is moved outwardly so that thefrictionally engaging surface of the lining 3 contacts with the brakingflange on the drum. As the lining is worn down it is necessary tomove'the shoe a greater distance outwardly to insure this frictionalcontact. In the present invention use is made of this differentialdistance resulting from wear on the lining to indicate such condition ofwear. VAs shown in Figure 1 this may be done by placing on the backingplate 4, a strip of di- Kelectric material 5. This may be secured to theelectric platev there is provided a metallic contact 1, which isconnected through the stud 8 to a conductor 9. This conductor isconnected at one terminal to a galvanometer indicator I0. 'I'he otherterminal of the indicator is connected through the conductor Il andsourceof currentA I2, to the ground. The source of current may be asmall battery supplying only sufficient current'to operate theinstrument. If desired the current may be taken from the storage batteryof the car. The electrical conductor 8 is suitably insulated irom thebacking plate by the insulated bushing i3.

As will be appreciated the purpose of the foregoing apparatus is toprovide for the establishment of .an electrical circuit when contact ismade through the contact 1. When such con- -tact is established thisfactor is indicated by deilection of the needle I4 on the instrument.

A simple method of establishing such circuit comprises providing ametallic conductor on the brake shoe so positioned and arranged as tomake contact with. the member 1 when the lining is worn down beyond thepredetermined safe degree. The apparatus as shown in Figure 1maycomprise a sleeve I5 of suitable conductive material which isconnected at one end, through the in termediacy of the screw I6, to theshoe and which at its other endreceives the yspringpressed contactplunger grounded at I1.

The operation of this structure will have been appreciated from theforegoing description. During the normal operation, and when the brakelining is in good condition, that `is to say is relatively thick, theshoe is moved outwardly towards the braking flange and the plunger I5rides only on the insulated section of the member 5.

However, as the lining becomes worn down the member I 6 movesprogressively outwards and finally contacts with the member 1. Thiscloses the electrical circuit, and operates the pointer Il.

The pointer is thrown over to the opposite side of" lthe dial to thesection marked thin thus showing that the lining has been worn down sothin thatreplacement is desirable in order iirst to 1nsure efllciency oibraking and second to prevent scariilcation of the drum.

The'embodiment of the invention previouslyv described indicates only twoconditions, that is to say a good condition and a poor condition of thebrake lining. If desired, 4the progressive diminutionin the thicknessvof the lining may be indicated. This may eiIectively be done byinsertingv the` resistance I8 in the circuit. This may comprise acontinuous helical resistance as shown' in Figure 2. The dial of theindicator is calibrated as shown at I9. Any point which vcorresponds tothe relative diminution' in the thickness in the lining, orotherelements of the circuit are substantially the same. The backing Yplate is provided with the insulated plate i, upon brake, the plunger I6will ride upon the insulated portion' of the plate 5. As the liningbecomes worn down, however, the lplunger will contact with 'one endofthe continuous' resistance I8. In thisA circumstancethe current flowsthrough the entire resistance andthe needle is deflected the minimumamount. However, as the lining wears down the resistance will beincreasingly cut out so as to insure a greater deflection of the needle.If desired also the relative condition of the four brakes of the vehiclemay likewise be indicated. Sucha structure is shownin Figures 3 I6. Thismetallic plunger is` and 4. In this arrangement the indicator isprovided with four pointers I9, which cooperate with sectionsof the dialcorresponding respectively to the four wheels of the vehicle. Each oneof the shown in Figure 2 except that upon application of the brakesfasimultaneous reading for all four of the wheels is obtained. Thegalvanometers may be enclosed in any suitable casing 22 and positionedadjacent the dash. The indicator III may be suitably mounted. on thedash 23.

It will be seen that by the employment of a mechanism of the typedescribed the relative conditionof the brakes on any one, or all of thewheels of a vehicle may be indicated to the driver during the operationof the car and will disclose the necessity of replacement of the brake1inings before the thickness ot` such linings are dangerously reduced.

While speciilc embodiments have been shown it will be understood thatthese are given merely as examples as it will be appreciated that otherparticularmechanisms may be employed. Thus, in lieu of the electricalarrangement other mechanical or hydraulic devices may be employed toindicate and/or measure the wear on the linings and to this extent showthe relative condition of the brakes. f

I claim:

1. An internal brake comprising a rotating drum, a stationary backingplate, a relatively non-rotating brake shoe mounted on said backingplate and having a friction lining and adapted to be moved into and outof engagement with said drum, a pair of contacts radially spaced andcarried by said plate and shoe respectively and housed within said drumand backing plate and adapted to electrically contact upon movement ofsaid shoe relative to said plate to an abnormal extent due to wornfriction lining, and an electrical indicating circuit connected to saidcontacts.

y2. An internal brake comprising a rotating drum, a stationary backingplate, a relatively non-rotating brake shoe mounted on said backingplate 'and having a friction lining and adapt ed to be moved into andout of engagement with said drum, a resistor and sliding brush carriedby said plate and shoe and arranged for relative movement and housedwithin said drum and backing plate, an indicating circuit and source oielectrical energy connected with said resistor and brush, whereby theindicating circuit may be directly aected `by relative radial movementof said shoe and plate, s'aid brush being adapted toslide clear of saidresistor when said brake shoe .is in released position to open saidelectrical circuit.

RAYMOND J. NORTON.

